macOS / iOS JavaScriptCore - Loop-Invariant Code Motion (LICM) Leaves Object Property Access Unguarded

While fuzzing JavaScriptCore, I encountered the following modified and commented JavaScript program which crashes jsc from current HEAD and release /System/Library/Frameworks/JavaScriptCore.framework/Resources/jsc: function v2trigger // Force JIT compilation. for let v7 = 0; v7 1000000; v7++ if...